s = input()
cww = "cww"
idxlist = [0]
for c in cww:
    idx = s.find(c)
    if idx == -1:
        print(-1)
        exit(0)
    idxlist.append(idx + idxlist[-1] + 1)
    s = s[idx+1:]
print(idxlist[-1] - idxlist[1] + 1)